<template>
    <el-color-picker :value="themeColor" @input="changeThemeColor($event)"></el-color-picker>
</template>

<script>
import {mapGetters} from 'vuex'
const version = require('element-ui/package.json').version
export default {
    name: "theme",
    computed: {
        ...mapGetters([
            'themeColor',
            'ORIGINAL_THEME'
        ])
    },
    mounted() {
        this.$nextTick(()=>{
            this.updateTheme(this.themeColor,this.ORIGINAL_THEME)
        })
    },
    methods: {
        changeThemeColor(v){
            if(!v) return;
            this.updateTheme(v, this.themeColor)
            this.updateTheme(v, this.ORIGINAL_THEME)
            this.$store.commit('user/SET_THEME_COLOR',v)
        },
        updateTheme(val, oldVal) {
            if (typeof val !== 'string') return
            const head = document.getElementsByTagName('head')[0]
            const themeCluster = this.getThemeCluster(val.replace('#', ''))
            const originalCluster = this.getThemeCluster(oldVal.replace('#', ''))
            const getHandler = (variable, id) => {
                return () => {
                    const newStyle = this.updateStyle(
                        this[variable],
                        originalCluster,
                        themeCluster
                    )
                    let styleTag = document.getElementById(id)
                    if (!styleTag) {
                        styleTag = document.createElement('style')
                        styleTag.setAttribute('id', id)
                        head.appendChild(styleTag)
                    }
                    styleTag.innerText = newStyle
                }
            }
            const chalkHandler = getHandler('chalk', 'chalk-style')
            if (!this.chalk) {
                const url = `https://unpkg.com/element-ui@${version}/lib/theme-chalk/index.css`
                this.getCssString(url, chalkHandler, 'chalk')
            } else {
                chalkHandler()
            }
            const link = [].slice.call(
                document.getElementsByTagName('head')[0].getElementsByTagName('link')
            )
            for (let i = 0; i < link.length; i++) {
                const style = link[i]
                if (style.href.includes('css')) {
                    this.getCssString(style.href, innerText => {
                        const newStyle = this.updateStyle(
                            innerText,
                            originalCluster,
                            themeCluster
                        )
                        let styleTag = document.getElementById(i)
                        if (!styleTag) {
                            styleTag = document.createElement('style')
                            styleTag.id = i
                            styleTag.innerText = newStyle
                            head.appendChild(styleTag)
                        }
                    })
                }
            }
            const styles = [].slice.call(document.querySelectorAll('style'))

            styles.forEach(style => {
                const {
                    innerText
                } = style
                if (typeof innerText !== 'string') return
                style.innerText = this.updateStyle(
                    innerText,
                    originalCluster,
                    themeCluster
                )
            })
        },
        updateStyle(style, oldCluster, newCluster) {
            oldCluster.forEach((color, index) => {
                style = style.replace(new RegExp(color, 'ig'), newCluster[index])
            })
            return style
        },
        getCssString(url, callback, variable) {
            const xhr = new XMLHttpRequest()
            xhr.onreadystatechange = () => {
                if (xhr.readyState === 4 && xhr.status === 200) {
                    if (variable) {
                        this[variable] = xhr.responseText.replace(/@font-face{[^}]+}/, '')
                    }
                    callback(xhr.responseText)
                }
            }
            xhr.open('GET', url)
            xhr.send()
        },
        getThemeCluster(theme) {
            const tintColor = (color, tint) => {
                let red = parseInt(color.slice(0, 2), 16)
                let green = parseInt(color.slice(2, 4), 16)
                let blue = parseInt(color.slice(4, 6), 16)
                if (tint === 0) {
                    // when primary color is in its rgb space
                    return [red, green, blue].join(',')
                } else {
                    red += Math.round(tint * (255 - red))
                    green += Math.round(tint * (255 - green))
                    blue += Math.round(tint * (255 - blue))
                    red = red.toString(16)
                    green = green.toString(16)
                    blue = blue.toString(16)
                    return `#${red}${green}${blue}`
                }
            }
            const shadeColor = (color, shade) => {
                let red = parseInt(color.slice(0, 2), 16)
                let green = parseInt(color.slice(2, 4), 16)
                let blue = parseInt(color.slice(4, 6), 16)
                red = Math.round((1 - shade) * red)
                green = Math.round((1 - shade) * green)
                blue = Math.round((1 - shade) * blue)
                red = red.toString(16)
                green = green.toString(16)
                blue = blue.toString(16)
                return `#${red}${green}${blue}`
            }
            const clusters = [theme]
            for (let i = 0; i <= 9; i++) {
                clusters.push(tintColor(theme, Number((i / 10).toFixed(2))))
            }
            clusters.push(shadeColor(theme, 0.1))
            return clusters
        }
    }
}
</script>
<style lang="scss" scoped>

</style>